"AFAIK the concepts of the stack and 'subroutine call instructions' existed before C because those concepts are also useful when writing assembly code [..]"
The stack principle was patented in 1957 by Friedrich L. Bauer.
It was well known before C but in 1957 it was considered noteworthy enough to justify a patent.
The stack principle was patented in 1957 by Friedrich L. Bauer. It was well known before C but in 1957 it was considered noteworthy enough to justify a patent.